1. Field of the Invention
The present invention relates to a lighting device, a liquid crystal element integrally provided with a surface light source, and a liquid crystal display device.
2. Description of the Related Art
Flat panel displays such as liquid crystal panels have been improved, and attempts have been made to improve image quality, reduce power consumption, and improve lifetime. On the other hand, various self-light emitting displays such as PDP (Plasma Display Panel), FED (Field Emission Display), SED (Surface-Conduction Electron-emitter Display), organic electroluminescence (hereinafter referred to as EL) display, and inorganic EL display have been studied, and some of them have been put into practical use. These displays using a self-light emitting display device have been developed for the purpose of breaking into the liquid crystal display market. One feature of these displays is that a thickness of a display portion of a product can be thinned because a backlight is not necessary like liquid crystal, which is advantageous in terms of power consumption.
Even to liquid crystal displays including a wide variety of products from small to large sized products in manufacturing techniques or infrastructures, the entry of the above-described self-light emitting display to a market is a threat, and a problem remaining in a display using a liquid crystal panel requires a response.
The above-described problem of the liquid crystal display includes the following problems: to reduce a space necessary for a backlight and power consumption for driving this backlight; to improve the loss of light other than polarization which needs light polarized as input light to liquid crystal, a cost increase due to a structure such as an optical film for making incident light uniform in the plane, an increase of space; and the like.
In order to solve the above-described problems, downsizing, high efficiency, and longer lifetime of a cold-cathode tube has been continuously developed. Instead of a cold-cathode tube, improvement of luminous efficiency of a light emitting diode has been studied, and improvement thereof has been advanced (e.g., Reference 1: Japanese Published Patent Application No. H8-248420). However, these light sources are a linear light source or a point light source, and a scatter plate having a strong scattering property or a light conducting plate is necessary to obtain uniform luminance.
Furthermore, in order to use light efficiently, there is a liquid crystal display in which multiple kinds of expensive luminance-increasing films are combined, arranged or the like between a light source and the liquid crystal panel. These films can transmit a predetermined polarized light component, the other component can be returned to the light source side, and light thereof can be reflected on the light source side and reused as light incident on the panel again by changing a polarization direction.